Fix macOS tray, update prompts, and provider link routing - #25

What changed

• Resize the tray image to 16×16 on macOS before creating the Electron Tray, while leaving other platforms unchanged.
• Remember the version of an update dialog dismissed with Close or Go to Releases.
• Continue showing the sidebar update indicator, preserve Remind Tomorrow, and automatically prompt again when a newer release appears.
• Open ordinary HTTP/HTTPS links from provider webviews in the system browser while keeping recognized sign-in flows inside AI Gate with the shared provider session and existing confirmation dialog.
• Add Electron and renderer regressions for these behaviors.

Why

AI Gate was passing its 1024×1024 PNG directly to the macOS status item. On affected systems, that created a 1040-point menu-bar window that displaced or hid other apps' status items. The update dialog also stored no state when dismissed, so the same release reopened on every launch.

Version 4.7.1 also routed every HTTP/HTTPS pop-up from a provider webview into a small AI Gate window. The broad rule was introduced for OAuth, but it also captured ordinary links that should open in the user's default browser. Routing now recognizes authentication hosts and path segments, keeping those flows in-app while sending other web links to the OS handler.

Validation

• npm run build
• npm run e2e — 22 passed
• Targeted ESLint for the new popup routing module and tests
• Built and installed the signed universal 4.7.1 app on macOS; CoreGraphics reports a 32×24-point AI Gate status item on both displays instead of the previous 1040-point window.

Existing lint failure

• npm run lint still fails on upstream main with 71 existing errors and 15 warnings; this change adds no new lint findings.